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The UA-led Phoenix Mars lander mission — labeled a success by NASA officials — was a historic achievement for space exploration, but not necessarily because of what's being hailed by some as its biggest accomplishment.

While it made headlines around the world for becoming the first spacecraft to reach out and touch Martian water, scientists involved in understanding the red planet say insights into the chemical composition of the soil and other discoveries likely will bear the largest impact on theories about the planet.

Further, the mission's confirmation of water after satellites detected an ice layer just beneath the northern arctic soil will allow scientists to put more confidence in the data provided by experiments orbiting the planet, an important step in verifying theories about Mars.

And by having a successful NASA scientific mission run by the University of Arizona at an off-site location, Phoenix paved the way for other universities and research groups to take a more active role in space exploration, Mars experts independent of the mission said.

But perhaps the biggest discovery by Phoenix is the one that has yet to be made.

While the $428 million spacecraft shut down earlier this month when the lander ran out of power, the work of those involved with the science mission is only beginning. Results from Phoenix must be replicated in laboratories, data analyzed and papers written.

It could be months, perhaps even years, before scientists are able to fully understand exactly what Phoenix found and whether the Martian north pole could ever have supported life.

Regardless of whether Phoenix can answer questions about Mars' habitability, the mission deserves its accolades, said William K. Hartmann, a senior scientist with the Tucson-based Planetary Science Institute who has devoted much of his career to understanding Mars.

"I think it was a great success, and it was a real model for how to conduct a mission and keep the public interested," said Hartmann, who wasn't involved in the mission. "We get so excited about the moment of landing, but people forget that it's six months later when discoveries are made."

Hartmann, who has worked on three other missions to Mars, said that, to him, the most fascinating discovery made by Phoenix was the chemical makeup of the arctic soil.

The presence of certain minerals likely indicates that liquid water interacted with the soil at some point, which opens the door to the possibility of life.

"As farmers in Western Arizona know, when desert soil is irrigated with water, the water soaks in and dissolves minerals, then evaporates at the surface," Hartmann said. "The same thing seems to have happened on Mars, so the minerals left behind tell us something about the mobility of the water and what minerals were available below the surface."

Hartmann's only criticism of Phoenix — which traveled 420 million miles before touching down on Mars in May — was not with the mission itself but rather with how the media reported some of its results.

A general perception among many members of the press was that Phoenix discovered water on Mars, when in fact it only confirmed observations of previous missions, Hartmann said.

"In that sense, we already had evidence of water, and that as you march from the equator towards the poles, it's pretty clear that there's ice," he said.

But because Phoenix was sent to Mars to find water, the excitement surrounding that confirmation was deserved, said Steve Ruff, a faculty research associate with Arizona State University's Mars Space Flight Facility who also wasn't involved with the mission.

Ruff, who has worked on several NASA missions including the Mars rovers, said the most exciting aspect of Phoenix is that it proved satellite observations of the planet's surface are accurate.

"For me, this notion of providing ground truth for orbital data is very important," he said. "Having a mission follow up an orbital discovery allows me to have that much more confidence in orbital data."

Given the volume of data from the several satellites around Mars, the example set by Phoenix may embolden other theories about where water may be on the planet.

"Now we can say that there are large parts of Mars that have permafrost — that's a profound result," Ruff said.

While the mission may have strengthened some theories about Mars, it muddled others. Previous information from other landers and rovers has shown that the planet's soil is acidic, Ruff said.

But the soil around Phoenix appears to be almost the opposite, indicating that Mars' soil might be more diverse than previously thought.

"It certainly forces scientists to rethink our theories," Ruff said. "Maybe we go too quickly down that path."

As for the larger questions of whether Phoenix has discovered a habitable zone or a soil that could support life, Ruff remains skeptical.

So does Peter Smith, the UA's lead scientist for the mission.

Smith said that Phoenix — the first NASA mission to be led by a public university — ultimately will be judged based on the truth it unearths.

While early results indicate that the northern plains had the potential for being habitable at some point, Smith isn't ready to make that theory official.

"The preliminary interpretations are often not quite the full story," he said. "People so often ask, 'What are the final results?' but we've really only picked off the low-hanging fruit.

"The wet soil might have been conducive to life, though it may be that it was not," he said. "We're looking for true answers, and the jury's still out."